So-called three message signs are known. See for example Bergeron et al, WO 92/11621 published Jul. 9, 1992 entitled IMPROVED MULTI-MESSAGE SIGN. This patent illustrates an exemplary rotation mechanism for use with such signs.
Illumination of such signs has been a problem, especially where the sign itself is to provide the illumination for reading the sign at the message display. Three methods of such illumination are known.
First, it is known to illuminate internally each of the rotating message displays, by placing a light source, such as a fluorescent bulb. Unfortunately, placing a fluorescent bulb interior of a triangular and rotating sign message display gives severe difficulties both in the wiring of the fluorescent bulb and the mechanics of maintaining and or replacing the bulb within the rotating vane.
Second, and in order to prevent stray light from escaping from the rotating sign message displays, it has been known not only to mount the fluorescent bulbs interior of a rotating sign message display but also to provide internal light baffles in such signs. These baffles serve to block light from impinging on sides of the rotating sign message displays not exposed for view and concentrate light only on the message surfaces exposed for view. These baffle systems further complicate the mounting of the fluorescent bulb interior of the vanes.
Third, and in a move to avoid the complication of mounting fluorescent bulbs interior of the rotating sign message displays, it is known to mount lighting sources at the ends of the rotating sign message displays. Light from these ends then propagates interior of the triangular rotating sign message displays, illuminating all message surfaces. Such illumination systems again complicate sign construction as the necessary interval for both the generation and the introduction of light must be preserved in an area where the intermittent rotating motion of the three-message display array occurs.
A common form of advertising is the use of "menu boxes." These menu boxes are typically mounted in places of business. These boxes usually have a recessed interior illuminated by a plurality of fluorescent bulbs. In their use, the boxes are provided with a translucent face through which light from the fluorescent bulbs is diffused. When a translucent message covers the exterior of such menu boxes, the translucent message is back illuminated rendering its message visible to viewers.